suspicious RCU usage from smack code

[John Garry]

Hi guys,

JFYI, When I enable CONFIG_PROVE_RCU=y, I get these:

[    0.369697] WARNING: suspicious RCU usage
[    0.374179] 5.6.0-rc3-00002-g619882231229-dirty #1753 Not tainted
[    0.380974] -----------------------------
[    0.385455] security/smack/smack_lsm.c:354 RCU-list traversed in 
non-reader section!!
[    0.394183]
[    0.394183] other info that might help us debug this:
[    0.394183]
[    0.403107]
[    0.403107] rcu_scheduler_active = 1, debug_locks = 1
[    0.410389] no locks held by kthreadd/2.
[    0.414770]
[    0.414770] stack backtrace:
[    0.419636] CPU: 0 PID: 2 Comm: kthreadd Not tainted 
5.6.0-rc3-00002-g619882231229-dirty #1753
[    0.429204] Call trace:
[    0.431924]  dump_backtrace+0x0/0x298
[    0.435990]  show_stack+0x14/0x20
[    0.439674]  dump_stack+0x118/0x190
[    0.443548]  lockdep_rcu_suspicious+0xe0/0x120
[    0.448487]  smack_cred_prepare+0x2f8/0x310
[    0.453134]  security_prepare_creds+0x64/0xe0
[    0.457979]  prepare_creds+0x25c/0x368
[    0.462141]  copy_creds+0x40/0x620
[    0.465918]  copy_process+0x62c/0x25e0
[    0.470084]  _do_fork+0xc0/0x998
[    0.473667]  kernel_thread+0xa0/0xc8
[    0.477640]  kthreadd+0x2b0/0x408
[    0.481325]  ret_from_fork+0x10/0x18

[   18.804382] =============================
[   18.808872] WARNING: suspicious RCU usage
[   18.813348] 5.6.0-rc3-00002-g619882231229-dirty #1753 Not tainted
[   18.820145] -----------------------------
[   18.824621] security/smack/smack_access.c:87 RCU-list traversed in 
non-reader section!!
[   18.833544]
[   18.833544] other info that might help us debug this:
[   18.833544]
[   18.842465]
[   18.842465] rcu_scheduler_active = 1, debug_locks = 1
[   18.849741] no locks held by kdevtmpfs/781.
[   18.854410]
[   18.854410] stack backtrace:
[   18.859277] CPU: 1 PID: 781 Comm: kdevtmpfs Not tainted 
5.6.0-rc3-00002-g619882231229-dirty #1753
[   18.869138] Call trace:
[   18.871860]  dump_backtrace+0x0/0x298
[   18.875929]  show_stack+0x14/0x20
[   18.879612]  dump_stack+0x118/0x190
[   18.883489]  lockdep_rcu_suspicious+0xe0/0x120
[   18.888428]  smk_access_entry+0x110/0x128
[   18.892885]  smk_tskacc+0x70/0xe8
[   18.896568]  smk_curacc+0x64/0x78
[   18.900249]  smack_inode_permission+0x110/0x1c8
[   18.905284]  security_inode_permission+0x50/0x98
[   18.910412]  inode_permission+0x70/0x1d0
[   18.914768]  link_path_walk.part.38+0x4a8/0x778
[   18.919802]  path_lookupat+0xd0/0x1a8
[   18.923871]  filename_lookup+0xf0/0x1f8
[   18.928136]  user_path_at_empty+0x48/0x58
[   18.932590]  ksys_chdir+0x8c/0x138
[   18.936366]  devtmpfsd+0x148/0x448
[   18.940146]  kthread+0x1c8/0x1d0
[   18.943732]  ret_from_fork+0x10/0x18

I haven't had a chance to check whether they are bogus or not.

Thanks,
John